Tension testing apparatus



Dec. 16, 1952 L. F. GUIMBRETIERE El AL 2,621,512

TENSION TESTING APPARATUS 8 Sheets-Sheet 1 Filed Dec. 26, 1947 Dec. 16, 1952 F. GUIMBRETIERE ET AL 2,521,512

TENSION TESTING APPARATUS Filed Dec. 26. 1947 a Sheets-Sheet 2 Fig.2

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Dec. 16, I952 1.. F. GUIMBRETIERE ET AL 2,621,512

TENSION TESTING APPARATUS Filed Dec. 26, 1947 8 Sheets-Sheet 3 //VVEN Tags t u a n Dec. 16, 1952 1.. F. GUIMBRETIERE ET AL 2,621,512

TENSION TESTING APPARATUS Filed Dec. 26. 1947 8 Sheets-Sheet 4 V 0 940 0'0 60 Ina/20140160 I60 //V/EN TOELS I ead M Ac or-her 'In fut,

Dec. 16, 1952 F. GUIMBRETIERE ET AL 2,621,512

TENSION TESTING APPARATUS 8 Sheets-Sheet 5 Filed Dec. 26. 1947 rf farney in fad,

Dec. 16, 1952 L. F. GUIMBRETIERE ET AL 2,521,512

TENSION TESTING APPARATUS Filed Dec. 26, 1947 8 Sheets-Sheet 6 nvrz/vw s: hgz Ki n v in fact.

L. F. GUIMBRETIERE ET AL 2,621,512

TENSION TESTING APPARATUS 8 Sheets-Sheet 7 Attorney 1'): (kc/t Dec. 16, 1952 Flled Dec 26 1947 [NYE/{TORS Dec. 16, 1952 L. F. GUIMBRETIERE ET AL TENSION TESTING APPARATUS Filed Dec. 26. 1947 8 Sheets-Sheet 8 ine nts depending on the value Patented Dec. 16, 1952 1 PATENT OFFICE a "42521512 "rnns roN Tr-E'STIN APPARATUS Louis Francois fGuirnbretiere, Montfaucon; i and EugeneJeanfSorez, Roubaix Franc .n licationfnecember 26, 1947, seria1 No.'7.9,4,925

, Jn Franee'Decelnber 27t1946 1 The machines and apparatuses known 'tothis day 'that servejfor any kind of "industrial control in'fdustriartests relating r 1 instance to elongati'on'be 'fore breaking, breaking load; power ab- ,sorbedwbefore breaking, elastic limit, breakdown yfolta ge; electric conductivity .and' the like, are

generally designed" for the execution of. a cornji ar'ativelyreduced-number ofptests'; "They are generallyfnot automatic and Q 1 .61? give out .ldi-

j 'ctiy' n a statistical forin theresults of theigsts executed. i r

sequentexploitation.

' Our inventionlhas forits cbjeclt a g'eneral methjf examine te tin na ,es n m cjtly statisojall m te.-

iticaTresultsiand thatlare n at e t r al e t'edaHM n 11 attestin -It Q VQ'TS h j Si ap ar tuse and machi i fiained i 'wb nc i hsu rin i es Ll fi imfibn sessen A gu in t mu g points: Y

The magnitude or magnitud megsured are trans latedjnto 'displacements ef oneor moremov- "able members-the amplitudes said displace.-

, .I m nitud ormagnitudesconsidered. I These jdisplacernents appear materially and 'arefrecord'ed at the end of'eaehte's'tj:

(a) Ei-ther "through the. operation of suitable measuring ormeteringmeans'; 1 Q

' (1)) Or velse ley the dropping o f balls'into one orjnrore ehannelsrigrooves;tuhesor the like equiv.- alentdevices' theyorder ascribed to which cor-re.- sl iqnds to the valueof the magnitude to be measured;. v w I (c-) lo r hy the suitable inscription on pr per-r :f ratine n or more gra s that recordein ltheir torder of execution the, successivezresults .z(d)' Or :throuh the periodical 4photographicor printed recording. of the partial results recorded iby metering means; 4

21 Claims.

2 "The adaptation to' any desired value of the speedqfapplication of the tested'stre'ss j j "f'I he' adjustment to any desired value 0i the nurnber of tests provided fora series of tests} Theautornatic ejection of asample after each lThB interruption ofthe operation of the apparatus when the predetermined nurnber of -te'sts 'hasjzbeen' executed. r i v ter the execution of a complete series'of tests it is possible to obtain further results as follows: The-distribution of the/balls dropped intdthe 'difiere nt'receiving grooves providesfin an immediate' mariner-a material showing of the total'statistic s-of the'series of-te'sts: the use qffseriejslof balls that are differently markedfleithera's concerns their color'ortheir nature allows studying within the total statistics, separate subordinate 'buti'on'of'the-difierent series'of balls;

' The numeric indications provided Joy the totalisi'ng meters provide the sum of the elementary 'results whereby it is possible-V to ascertain-the -1'nean value of--the tests; theirdispersii'on andthe "rate of said dispersion. "The exploitation of 'the perforated graphs by means 'of' 'a' suitable automatic analyser allows the statistical definition of the systematic and periodical surnames that may appear in the'prituduction of the-samples that are being studiedf'ev'e'n when they are concealed by the Gauss dispersion ofthe-elementary tests. 4 By way of examples of application of-10i1r.1improved method andby no means in aiimitatiVe gs'ensewe havedescribed hereinafter ariautpm'at =ic statisticdynamometer'for the tractiqnafltest of material under the form ofWhen-threads,staple strips or thelike'j; Inthe accompanyingdrawing's: Fig, -1-il 1ustrates an automaticsta'tis'tic dynam m e of th s e- -Figr2-is a detail thereof. I

=FigL-3 illustrates the curve correspondingto the law 'of elongation 10f thespring therein with jet- Fig. 11 relates to means for integrating the work spent in each dynamometric test.

Figs. l2, l3, l4, l and a illustrate diagrammatically various detail arrangements that may be associated with the machine.

Figs. l6, l7 and 18 relate to still further auxiliary details.

Fig. 19 is a general schematic view of the machine.

Returning to Fig. 1, our improved automatic statistical dynamometer as shown diagrammatically in said figure includes a suitably gauged dynamometric spring I connected on one hand with the point 2 of a pendular lever 3 that is substantially stationary and on the other hand to an arrangement submitting said spring to a tractional stress in accordance with a law such as that governing the speed of application of the force as a function of time, said tractional stress being selected in accordance with the nature of the tests that are to be executed, for instance a winding of the rope I connected with the spring over a suitably shaped cam 5 that submits the dynamometric spring I to an elongation which is a function of the shape of the cam 5, said elongation resulting in a force applied to the substantially stationary pendular lever 3 that increases in proportion with the rotation of the motor 233 which drives the cam 5 through a worm and gear arrangement 234, 235. Said rotation being constant all over a test, the rotation of the cam is in proportion with time, the shape of said cam introducing the function of time. The pendular lever 3 carries a clamp 6 that is also substantially stationary and between the jaws of which the thread to be tested 1 is introduced through a suitable leading device.

The other end of the wire I is clamped between the jaws of the movable clamp 8 that is secured to the carriage 9. The carriage 9 is urged rearwardly by a counterweight In or by any other equivalent device. It is driven forwardly by a winch II operating at a variable speed and producing the displacement of the clamp 8 and thereby a lengthening of the test thread 1 during operation. The variations in speed of the winch II may be controlled in various manners through the agency of a suitable auxiliary motor as controlled by the exceedingly small modifications in position of the substantially stationary clamp 6.

The auxiliary motor M may be controlled for instance as follows:

The displacements of the substantially stationary clamp 6 may be of a magnitude as small as may be required by the nature of the material that is being tested and this is obtained by means of a suitable distribution of the points 2 and 6 along the pendular lever 3. This pendular lever 3 controls through a lever 230 pivoted at 23I on a shaft and which is applied at 232 against said lever the opening or closing of a mercury valve I2 in which the mercury may be replaced by any other suitable electrically conductive liquid.

According as to whether the pendular lever 3 rocks in one direction or the other, the valve I2 opens or closes as illustrated in Fig. 2 and the output of mercury through the superposed nozzles I3 and I4 varies. The level of the mercury in the column I5 rises or sinks and short-circuits thereby a variable fraction of the resistances I6. These variations in the resistances I6 are made use of in the adjustment of the speed of the winch II.

Suitable auxiliary devices such as a circulating pump I1, settling tanks I8, a constant level container I9 ensure stability of operation of the machine. In brief, the speed of elongation of the thread under the action of the carriage 9 is thus controlled by the law governing the application of the load as a function of time, said law being incorporated in the characteristics of the spring I and in the outline of the cam 5. From the preceding disclosure, it is apparent that:

The path travelled over by the carriage 9 is proportional to the elongation to which the sample I! is submitted;

The amount of expansion of the spring I is proportional to the tractional forces exerted on the thread 1. I

It should be noticed that suitable auxiliary arrangements allow the adjustment to any desired extent of the ratio between the displacement of the carriage 9 and the elongation to which the test sample has been actually submitted. By way of example and by no means in a limitative sense, we have illustrated in Fig. 1 a differential winch 20, 20a with an adjustable pulley ratio, associated with an also adjustable lever I00.

The curve relating the ratio between the load of a spring and its elongation appears generally under the form of the curve of Fig. 3. It is of interest to use the spring in the rectilinear part AB of its characteristic. To this purpose, the pendular lever 3 is provided with an adjustable counterweight 2| or any other suitable device so as to tension the spring I before the beginning of the tractional operations applied to the thread 1.

The displacements of the carriage 9 are controlled by the winch I I that may be carried either by the carriage itself or by the frame of the apparatus. The speed of displacement of the carriage 9 may be adjusted to the variations in position of the pendular lever 3, for instance:

Through the insertion of the above-mentioned resistances I6 such as shown in Fig. 1 in the electric feed circuit of the motor driving the winch II; or through an electromagnetic braking of the planet wheel of a suitable sum and planet gear, or again through any suitable other method.

By way of example and by no means in a limitative sense, we have disclosed hereinafter means for executing the method consisting in braking a planet pinion (see Fig. 4)

The pulley 22 drives a sun-and-planet gear 26 and is driven itself by a motor M that may either be the general motor of the dynamometer; Another pulley 23 keyed, to the auxiliary shaft of the sun-and-planet gear or an auxiliary motor.

is operatively connected with a metal disc 24 rotating between the poles of an electromagnet 25. The latter is fed with current adjusted at any moment through the insertion in its circuit of the variable adjusting resistances I6 that are controlled as disclosed hereinabove through the operation of the mercury valve system I2I3 under the control of the lever 3. The energizetion of the electromagnet varies thus instantaneously in accordance with the position of the pendular lever 3 that governs the operation of the resistances I 6 so as to produce a more or less energetic braking of the disc 24. It is apparent that the output shaft 21 of the sun-and-planet gear is controlled differentially by the control bevel gear on the left hand side submitted to the action of the metal disc and by the driving bevel gear to the right, and that said output shaft controls in its turn the Winch I I.

essa-sis the spring I by the simultaneous elongation of the test thread 1. r

I The operation of the dynamometer is'as follow's. w h

First operation: Traction exerted on the 'sample'and dynamometric measure. The winch driving the cam 5 produces an expansion or-the spring I in accordance with the outline selected for the cam. During said operation the 'movement of the carriage 9 progresses, said progres "sion under theaction of the motor M being such thatthe end of the sample I in the clamp 6 is stationary, the other end of said sample being 'clamped by the clamp 8 the position of which is controlled through the difierential winch'20, 200. by the progression of the carriage 9, the displaceinent of the carriage 9 being a function of the expansion of the sample 1. At the moment of the breaking of the sample. the pendular lever 3 is dynamically submitted to theaction of the spring I. This produces a closing of the auxillary'switch 69 whereby a suitable system of relays fully described hereunder with reference to Fig. 1'7, is caused to produce a reversal in the operation of the motor or motors incorporated in the machine. Thewhole machine including the means for measuring the elongation and the arrangement for measuring the forces returns to zero.

Recording of the breaking forces: The device for-recording the breaking forces includes without this enumeration being at all limitative .any of the following arrangementsf A ball distributing; conveying and receiving system as shown in Fig. A graphas illustrated in Fig. 6;

Ora perforating recording system as shown in Fig.7. The ball'distributor 28 described hereinafter asa' first form of execution or the recording means of the first type is designed so asto release a ball at'the'beginning' of each test (Fig. '5).

The *ball conveyor may for instance be constituted by a movable carriage 29 provided with a feed hopper 30 and a discharge port 3| the opening' of which is controlled by an electromagnet '32 the circuit of which is controlled in its turn by-the switch 69 actuated by the rocking of the lever'3i The ball receiver is then constituted by a-girooved plate 33 assuming a sloping position or'jby a series of parallel transparent tubes or any like-arrangement. The order of said grooves is such that they correspond to the successive breaking ldadsof which it is desired to form statistics.

As soon as a dynamometric operation begins the plate 236 of the distributor 28 rotates by a turn allowinga ball to'fall into the h pper 30 pot the carriage 29. Said carriage being inserted in the wire 4 (as shown in Fig. 19) its advances whenthe force applied to the sample 1 increases, the abscissa of the discharge port 3| of the hopper being thus at every moment proportional to t'he for'ce to which the sample 1 is submitted at the moment considered. 'At the moment of the breaking of the sample 1, thependular lever 3 '(Fi 1) returns-suddenly back and rocks so as to control the switch 69 which latter in its turn produces through the energization of the elec tromagnet '32 which is fed through a circuit 231 6 controlled by the switch 69 the dropping of ball into the groove corresponding'to the flnal stress exerted afterwhich the carriage 28??? turns at an accelerated speed to its starting' point. This being performed, the cycle of operations be;- gins over again. I H

The accumulation of the balls'in'the difierent grooves of the plate 33 forms a material visuali zation of the statistics concerningthe tes they are progressing. V m

Instead of the above describedball'cohvdr we may use a graphical recording device cgrh prising a recording stylus 34' cooper tingwitna paper strip 35. k k

During a test, the relative displacements of the stylus 34 with reference to "the record paper35 are at every moment proportional tofthe stress exerted on the sample I the stylus 34 being 111- serted in the wire 4 which extends the spring (see Fig. 1'). On the other hand, after each test. the strip of paper progresses through a cons 12 length this being obtained through 'a ratchet wheel 240 which is turned by'ia certain'angle after each test. The juxtaposition of th 'successive lines drawn by the stylus 34 on the paper'35 provides a chronological graph of the seriesfloftests executed by the machine. I

As stated, the recording may also be excepte by means of a perforating'recording system that may as in the example illustrated 'in Fig. 7 include a punch 62 and a recording strip 63. c U

During the execution of a test, the punchfii moves above the strip 63 without touching it and the relative displacements of saidmembersa're at every moment proportional to the stressesto which the sample I is submitted. At the moment of the breaking of the sample 1, the rocking'o f the pendular lever 3 leads to the engfagement qf the punch 62 into the strip 63 through thefcnere gization of a suitable electromechanical device 65, 66, 61 the electromagnet 61 ofwhich is fed by an electric circuit 231a controlled by the contact 69. The perforation being thus'execu'ted, its'dis'; tance from the point registering with the p' oh at the starting of the movement is proportional to the breaking load of the sample '1 and therecording device returns then to zero Whilethe strip 63 advances through one step at'least to the diameter of a perforation so as to avoid thetearing' of the paper. 7 y

We will describe at the end of the-present specification another form of execution of such'a statistical perforating device.

Electrical recording of the elongation under the action of the forces exerted. We will "first recall to mind that the carriage 9 progresses through amounts equal or prcpo'rtionaij to the extension to which the sample 1 is submittedgas the other end of the sample carriedby the clamp 2 may be considered as stationary. The'electrlcal recording means is constituted as follows: I

The carriage 9 (Fig. 8) carries an angularly adjustable arm 39 on which'mayresthorizontal rods 40a, 40b,- 40c, 40d. Said rods'are'parallel to the path of the carriage 9 and are spaced' by equal amounts while their length varies by equal amounts from one rod to the next say by 10 mm. from one rod to the next. Under such conditions, the ends of the rods are :in alignment over a common straight line AB forming a certain angle a with the path of the carriage 9. Each time the carriage'a'progresses by said 10 mm. for instance, one of the rods 40 drops and closes an electric switch 4I (41a, -4Ib, etc.) so as to close "theelectriccir 7. cuit corresponding thereto. Each switch 4|, as shown in Fig. 9, feeds two electric pulse meters 42-43 of the type for instance of telephone call meters. Each meter of the series 42 (42a, 42b,

eto.) records once at the moment of each closing of the corresponding switch 4|. Each meter of the series 43 (43a, 43b) records a number of pulses that is proportional at each moment to the increase in force acting on the sample 1 measured since the moment of the closing of the corresponding switch 4!. These electric pulses are produced by a current breaker 44 operating at a rhythm depending on the law governing the application of the force to the sample I through the agency of the cam 5. Said switch actuator is driven by a pulley 242 driven by a pulley 243 provided with a ratchet Wheel forming non return device, said pulley being frictionally driven through a wire 4a drawn by the cam 5 and tensiled by a counterweight 244, the frictional connection and the non return ratchet wheel being provided to allow the return to zero without the switch being operated.

The operation of last described arrangement is as follows as apparent from Fig.

The elongation of each tested sample is indicated by the number expressed in lengths, of the meter of the series 42 that has been the last to operate during the test considered; the value of the elongation corresponding to one half of the interval separating two successive meters should be added.

Each meter of the series 43 records an abscissa starting from the point at which the elongation corresponding to its number is reached and t that extends from this point onwards up to breaking value. The numbers of pulses registered by the different meters of the series 43 are proportional to said forces and are expressed in grams.

It is possible to totalise the numbers given out by the meters of the series 53 that have operaLed so as to obtain an actual integration measuring the work absorbed by the sample before its breaking.

.It' is obvious that the relative position of the difierent rods 43 and of the bar 39 may be changed without any modification in the principle of the apparatus. Similarly the relative movement of the members 39 and 40 may be controlled either directly by the carriage 9 as shown or else through the agency of any suitable member assuming proportional displacements such as a camshaft or any like arrangement.

It has been stated that the arm 39 is angularly shiftable round a pivot 45 mounted on the carriage 9. Supposing b is the angle formed bylthe arm 39 with the direction of translation of-a carriage 9, the adjustment of the angle b--a may be obtained through a rotation of the-arm 39 round the pivot 45 and its final clamping so as to obtain any desired value for the value of the extension of the sample 1 that corresponds to the dropping of a given lever 40 and to the closing of a switch 4|. A suitable scale 46 gives out through more reading the value in millimeters for instance of the elongation that may be recorded by the drop-ping of a lever or bar 40.

Execution of the average graph binding force to elongation in the case of a series of dynamometric tests. The use of the numbers registered by the meters of the series 42 and 43 allows the execution of such an average diagram binding the forces to the elongations in a series of dynamometric tests.

The accuracy of the registration that has been just described depends obviously on the number of levers 40 and of meters 42 and 43 associated therewith. In practice a series of 25 levers and twice 25 pulse meters provides for each elementary test an accuracy of i2% as concerns elongation, i2% as concerns force and i470 as concerns breaking power. The total accuracy reached in the statistics of the tests is therefore very high.

Obviously, the number of levers and meters may be adapted to any requirements as to the accuracy of the measure.

The integration of the breaking work spent in each dynamometric test is possibly obtained in the following manner (Fig. 11). A plate 41 rotates at a speed proportional to one of the two magnitudes, force or elongation. In the drawings this disc is shown as rotated at a speed proportional to the elongation, its central shaft being indeed driven through a conical gear 245 fast with the shaft of the winch l l which moves the carriage 9 so as to counter-balance the elongation of the tested wire. A roller 48 driving a totaliser 49 moves over a radius of the disc 41 so that the distance between its contacting point and the center of the disc 41 may be at every moment proportional to the other magnitude, elongation or force. In the drawings this distance is proportional to the force applied, the roller being moved through a wire which is drawn by the cam 5 in accordance with the wire 4. Under such conditions, the totaliser 49 forms an integrator of the elementary breaking work. i

Statistical information as provided by. the above described machine, either under the form of a distribution of balls or of the execution of an average diagram associating forces and elongations or again under the form of pulse numbers recorded by meters, allows the automatic reckoning of statistical data such as mean value, absolute variation, relative variation, absolute probable variation, relative probable variation, absolute quadratic variation, relative quadrative variation, typical variation, variability, dispersion and so on. All these magnitudes are of considerable industrial interest.

The length of each sample may be adjusted to any desired value which is the same for a series of tests. The length of said samples has adirect influence on the dispersion of the results of the tests and forms thus an important criterion as to the grade of the material undergoing test. Moreover, this feature is of considerable interest when looking out for system atic or periodical variations ascribable to the method of producing of the thread or wire.

Auxiliary mechanical moeeme'nt Opening of the clamps 6 and 8 (Fig. 12) .--The opening of either clamp may be obtained for instance through the rotation of an eccenter 50 controlled by a lever 5|, a rope 52 and a winch 53 connected with the general control means 54 through an electromagnetic clutch 55. At a certain point of the return to zero of the recording system, an electric switch closes at 56 in order to energize the clutch 55. The winch 53 then winds up the rope 52 which raises the lever 5| and opens the clamp. The stroke of the lever 51' is limited by the de-energization of the electromagnetic clutch the circuit feeding which is opened through the rocking of the switch 51- at" the end of the'stroke of the-lever i controlling the eccenter 5D- and acting on said switch.

clamps 6 and 8' being open, the thread-laying device described hereinafter is started. At the end of its stroke, the thread-laying carriage 58 abuts against a lever- 59 through the 'stop- 60 carried thereby so as to provide the disengagement of the claw clutch 6| and the release of F the Under the action of suitable weights winch 53. or any other suitable arrangements, the levers 5| fallback and closethe clamps Band 8-.

Feeding and laying of the thre d 7 in the open clamps 6 and 8 (Figs. 13 and 14) .--The auxiliary thread feeding device may include forinstance clutch or any like system controlled by the movement of the lever associated with the clamps 6 and 8. When the clamps 6' and 8 have been closed again, the feed clamp I62 opens andreturnsto its starting position.

Feeding, twisting and laying of a spinning staple between the clamps fifiand 8;.-In the case; where the automatic statistic dynamometer is used for testing staples before spinning; the feed device disclosed precedingly' may be associated with a suitable mechanism forgivingthe textile staple a suflicient torsion. Said mechanism has for-its object to bestowon the; staple a cohesion such that itmay-suitably supportithe tractional' efforts impressed thereon'bythe machine.

A similararrangement may be used for the systematicstudy of tractional tests, the tractional strain being; for instance associated with atorsional or securing strain;

Arrangement for giving the, thread a constant tension at the beginning of-the 'test.-It is obviously important that; all the elementary tests of a given series may be executed under perfe'ctlyidentical experimental conditions. In

tions, the-arrangement 'showndiagrammaticallyin Fig; 14'. In this-example--the-' thread gwound off the reel 53 passes between the jaws of a clamp-16 i that is controlled"electromagnetically for instance and thenround a pulley ltfi'rigid with :allever that is submitted to a suitable load as shown at 1.5.9. When the conveyor carriage I64 comesnearer the thread drawing clamp 8, a contact .closes that produces the closing of the clamp 1.6] on the thread. The lever l59-is then operative and gives the-thread l thepredetermined, initial tension.

Arrangement for ejecting the sample fraction broken by :the test.-"When the'sample "1- has been broken, the movable clamp 8' should be freed from the fraction of broken sample. such asflthe end f ath-read by means of-a special arrangement that may be for instance that illust'rated in the following arrangement a s-shown in- Figs; -and 1.511. The jaw sis-tread auto- 10 matically of itsfraotion of sample through the sample-layin device.

Returning to'the means releasing the broken fraction held in the clamp 8, Figs. 15 and 1511 show a support 8| associated with an adjustable pivot 80 and carrying thevertical lever 84. Said lever'carries anadjustable pivot 19. and an ejector of broken fractions 85- and it is held vertically by a weight 86. Said lever is incurved downwardly into a U-shape, so that the ejector 85- may surround the jaws of the clamp 8. This double ejector 85 includes for each element a ring 89 fastened tothe lever 84 and to which is Between saidjaw 81 and a secured ajaw Bl. jaw 88 secured thereto is inserted a rubber sheet 16' folded back to form two plies and the-ends of which are clamped between the jaws 81- and- 88. Said rubber sheet forms an elastic ring] which surrounds the clamp 8 and the edges of which rub on the lateral faces of said clamp when the vertical lever 84 is pivoted. The clamp- 8 is-provided with an eccentric fastening member and a lever 5|. At a predetermind' pointof thelever 51 is pivotally secured a bent lever 1-1 carrying a stop 18 with a sloping edge. The

bentlever ends with a sloping part I03 adapted tobearat a given moment against the piv 88- on the support 8 I.

At the moment at which the sample is tobe changed, the eccentric 50 iscontrolled bya rising movement of the lever 5-l. The-lever as it moves carries along with it the lever 84 through the agency. of thestop l8 and of the pivot 19. The strap shaped end of the lever 84 is shifted off its position of equilibrium and carries along-with it as it movesthe remains of the sample-that has just been broken; it is released and returns to its position-ofequilibrium when the slope I03 on-the lever 11 comesinto contact with the pivot at thismoment thestop 18 passes out of reach of the pivot 19 and the lever 84 is thus released and returns-also into its position of equilibrium.

A suitable mechanism such as a conveyor belt removes the remains of the sample as they fall out of the-clamp '8.

The arrangement described with reference to Figs. 15 and 15a isprevented from operating in the case of-the dynamometer being used for ex amining elastic and permanent elongations without any-breaking o-fthe-samples.

Perforatingmeansfor the recordin strip-A form of execution of such perforating-means is illustrated in iss. 7 and 17.- A P1111611 St etches at a high speed at a small-distance from the chart to be perforated 63. It is hfild by a springv in said position and the control is providedby the,

then a, substantial pressure on the upper end of the rotary punch. Said punch perforates' the paper oft-he chart while continuing its rot tion and bearing against a removable part 68 made of wood orthelike suitable material. The switch 69 (Fig.1?) controlling'the electromagnet fil is closed by the shifting towards the right hand side of the pendul'ar lever 3 at the moment of the-breaking ofthe sample and-is almost immediately afterwards openedthrough the general reversal of the operation of the apparatus. As a matter of fact,--' as shown inFig. "17, the switch 69 is normally-open duringthe dynamometrictractional test while the second switch in series therewith remains operative under the action of the tension of the return spring ll. At the moment of the breaking, the pendular lever 3 rocks suddenly towards the right hand side and closes the switch 69 so that current feeding the electromagnet 61 may pass through the two switches '10 and 69. But the direction of rotation of the grooved pulley 12 controlled by the drivin shaft changes and through the agency of the cable M submitted to the action of a counterweight 13 opens the switch 10 and deenergizes the electromagnet. The pressure exerted by the lever 65 on the needle valve of the rotary punch 62 lasts only one moment that is sufficient for the perforation of a hole in the chart 63, which latter is suitably carried along by a mechanism to this purpose. For instance the driving means for the chart may be constituted as illustrated by two sprocket wheels 201-202 mounted on a spindle 203 that is rigid with a ratchet wheel 204. The spring 64 raises the rotary punch as soon as the current is switched off the electromagnet 61.

The body 15 of the perforator is adapted to move with reference to the chart B3 and the movements of the perforator are always proportional to those provided for the recording stylus or the like means 34 disclosed with reference to Fig. 4.

Obviously the above described perforator may be replaced by any other equivalent arrangement adapted to out clean edged holes in the chart without any burrs. The system for urging temporarily the punch 62 down by means of a perforating force may be obtained through the I agency of a delayed relay feeding the electromagnet 61, such for instance as a measuring switch with a limited closing time. Instead of being executed by means of perforations separated from one another, the recording of the tests may be executed as follows as shown in Fig. 18 the chart of which is driven exactly in the same manner as in Fig. '7,

The bevel-shaped perforator cuts at each test a slot through the chart paper. Between two successive tests, the chart advances through a step equal to the length of a slot. The operation of the arrangement is obvious and is such that the statistics of the tests are recorded under the form of a castellated track adapted to be applied subsequently with great ease through the agency ofa suitable analyser.

Device for returning to zero at an accelerated speed At the moment of the breaking of the sample 1, the pendular lever 3 is dynamically drawn back by the dynamometric spring I. This movement produces a general reversal of the machine for instance .in the manner to be disclosed now with reference to Fig. 16:

The motor 233 drives the cam 5 through an arrangement with a double electromagnetic clutch including a central disc of magnetic metal 95 rigid with a shaft 93 on which is keyed the earn 5, a shaft 250 driven by the motor 233 through a reductor 234, 235; on said shaft are keyed two pulleys one of the said rotates an electromagnet plate 9| in one direction and the other 25l rotates a second electromagnet plate 52 in the opposite direction at a higher speed. When the electromagnets on plate 9| are energized through the contactor 2| 5 (Fig. 19) the cam 5 rotates with a slow speed. and in a given direction during the dynamometric tractional operation. After a breaking of the sample 1 the plate 92 is energized in its turn through the contactor 224 while the circuit feeding the first electromagnets 9| is broken. As the plate 92 rotates in the direction opposed to the direction of rotation of the first plate SH and at a much higher speed, the machine returns to zero at an increased speed.

The above described device may be replaced for instance by a variable speed electric motor adapted to be reversed or by any other known speed reversing and changing means.

The dynamometer is designed and fitted for testing under similar automatic conditions a sample 1 of any length whatever. To this purpose, the pivot l0l of the lever I00 is adjustable as to position along a slideway I02 (see Fig. 1) so as to define the starting position of the clamp 8 as desired.

The above described machine records statistics of breaking forces under the form of A distribution of balls (Fig. 5);

A chronological graph (Fig. 6)

Or chronological perforations (Figs. 7 and 18).

Obviously statistics of the elongations may be recorded under the same conditions as the statistics of forces. The elements of such a recording and their manner of operating are identical to those already described and it is just necessary to mention the possibility of a double statistical equipment for our automatic dynamometer.

The total statistics of the breaking work is provided at the end of a series of operations by the reading of the indications recorded by the pulse meters. The recording of the total indications given out by the numeric dials of meters is not satisfactory for examining partial statistics of the breaking power. This drawback may be set aside by equipping the dynamometer with a suitable photographic apparatus recording periodically the indications of the meters. By way of example and by no means in a limitative sense, it may be mentioned that the so-called Robot cameras are particularly suitable for such applications. Another solution to be also considered as a mere example without any binding sense attached to it consists in using meters with numeric rollers designed in a manner such that they may print periodically their indications on a rec'- ord paper, this being somewhat similar to the arrangement of the so-called Printomax electric meters and apparatuses for instance.

The ball-receiving grooves may, if required, be provided with scales for instantaneously ascertaining through mere reading the number of balls carried in each grove. It is thus no longer necessary to count them separately.

These balls may either be spherical or else they viously depend on the very nature of said magnitudes.

Th auxiliary devices adapted to provide for automaticity of operation of the apparatuses and those adapted to adjust the speed of application of the test stress obviously depend on the thelstatistics that are being; performed; fI'hei chronological. IBOOrding-,jdfil{i-Qe$ whether pnd-er the:..fo rm of graphs, perforat ons or "photographs,

or; moving. pictures:.fo-rprints may be modified toxaiconsiderablegextent.v

The-number; size, color, nature andishape'of' theballs may be modified as desired.

What'we claim is;

1. .A machine; for, statisticalxtests; tabeaexe outed. chieily on wires. and. threads. comprisin elastic; means-noting on one. end. of: the .sample.

being tested, Vmeans for; controlling; the tension exerted bys'aid. elastic means accordancewvith predetermined. law; with jreierence to} time; m a s riv n the; other endof thesampleiaw v frgmithe. first end; to: produce an. elon ati .of' he asam le: i p osit on. t that: ex rted; by: the

e astic means and; m a s. controlled; by" li ht move nt p the first. endyo t e. samp eunde theaction off theelastio, mear aand. producing: an

cti of mstme on drivins' means th tzsuhstantiallyb-alances'. the action of the first. mende s m ans- 2; a n r st t t al. test tender r at d c ef y 1 i e d. hread c m r s m e .man5,- nd an i rlpr du ine a igh 51 6 1 reduction; between: said balancing means-andthedriving'means. A .13.; m e. for st nasa les of... wi h e ds and. the ikeqmate al c mp isin a eig e silb ste tiallv ve t c lever arr ged to El i tun a en ndo: which o e d the sample is deta-ohab1y..,secured, a carriage r adapted to move radially with .reference. to. the vertical lever and. to; which; the other: end or thje sam-ple is SEQ-Edd, means controlling; the.

m eme t o ai carria e; away rrom-said ve ticalle'ver f r n ate ion liiorce' onisaid sample a sprin ur nst e ev r awaviromrt carriage in the vertical 'p lanerof the sample,

i r controlling the. nsion .orthe shr ne:

in. accordance with aprcdetermined junction of.

time, a circuitjsy stem controlling the carriage e 1 m a d he variah e eshtanceim serted in. said circuit system andmeans cqntrolled s strby. the. vertical 'lever, andcgntrollirig; sai ancjejbr energizing said circuit to, an.

creasing:

extent "as the vertical lever is sh ted through;

smal p de rmined angles, awayjrom thecar:- ria e for providing equilibrium between tl1 e ac-.- tion of the spring and the:tension'dth ample.

"4; An automatic statistic 'dynamometer for:

samples of elongated material comprising a weighted substantially verticallever arranged to pivot. round one end and to which one endpi the 7 sampleis ile .wh b vv se ure ,,'a ,'car-riagedapted .to' move radially with; ref eren-ce tq I the vertical lever andfto which the other end; 01;

114.; the. sample is: secured; means. controlling; the: movement. or; said carriage away. from-said; vertiical lever. for. exertingextensional. iorceonxsfiddr. sample',,a spring urging the. lever away'fromzthe' carriage inv the; vertical. plane; of; the. sample; means for; controlling the. tension of thesprina in accordancewith a: predetermined functionxoii time, an auxiliary motor adaptedgtncontrol the;

movements of the carriage controlling means, as...

circuit Ieedmg said motor, arheostat controlling; said circuit and thereby the: speed of rotationcis. the auxiliary notor', and means, controlled; by; the movement of the lever and controlling; the; rhea stat and includinga channel; .means;for; causing: a streamgof mercuryt'o pass through .said ch'an-e nel, a; valve cooperating. with said .channelioiti adjusting thefl'ow of mercury therethrough.and?

means for operatively connecting'thelevenwithi said valve.

5... Amachine for: ascertaining the; 1 elongations of. samples of thread. or :the; like-material ,com zprising two clamps for the ends; of; thetsam'plee. a vertical. pivoting lever: to. which one.-c.1amp;is.1 secured,. a carriage. towhich the: other clamprisi rigidly secured, a. spring urging the; leven.;i.n....o,-;. sample tensioning direction, means controlling; the stretching-of the spring in, accordancerwithv a predetermined function ofitime, means drivin the" carriage radially away from the;.levera.fortensioning the sample in oppositionto the spring; an electric motor: and speed'reducingmeans. sociated therewith. for controllingythe lastmenrtioned means, a potentiometric system: contro'lledi by. the vertical lever. when urged by. the: spring:

, through.predeterminedlangles, a. circuit contro1;-.

lingthe speed of themotor and iniwhicht-saidz potentiometric: systemis: inserted. for." a-diustmjg: the energy of. the current. flowing-s through. it m. accordance: with the; angular position.assumedirby" thehlever.

6. A. machine for ascertaining the. elongations: of. sampleslof thread orrthe like material. come prising twoclampsgforthe ends of the-Hsampla; a vertical pivoting lever. to which oneclamp: is".

secured,. a carriage to. which theother"clamp;is rigidly secured, "a spring; urging the lever:. -in::a

sample tensioning direction, means controlline the stretching of. the. spring: in accordance; with a predetermined function-of time, "-meansidrlving; thepcarriag'e radially away from "the-.leveffor; tensio'ning the; sampleinopposition toztlie sprina. an: electric motor and speed reducingr means asssociated therewith; for controlling the: l'ast' men tionedmeanaamercury columnfmeansfiord'auseing the" mercury to pass throughsaidsxcoluninijai valve; controlling the outlet of saidcolumngaz, mercury filled-vat in which: said columnzdimh. means whereby the, angular "posltlonfflffthfiifiYQKS controls. the position ofthervalve:withrreierencer to-thelotver end of the column, and:thereby. -thelevel of the-mercury insaid vat, a circuitoo trolling the motor and including a-.-pl,u rality1 I" horizontal resistances inserted in parallel in; the:- circuit and located in the vatto lie-immersed to a. varying extent by the: mercury, jthe totals-resisteance of the circuit. and thereby. the speeds-of the motor. fed by-tlrecircuit depending on; theflevel reached by the mercury in the vat with reference to the horizontal resistances.

'7. A machine forascertaining. the .elonj ations: of samples: of thread or the like:- material12cmprising two clamps for'the. ends of the Sample; a vertical pivoting lever to which .;'one; clamp is, secured, a carriage. to;which;the::other--clamp:=-

is rigidly secured; a; sprin urging, the leverrzins a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, a sun and planet gear, means for driving the input thereof at a constant speed, a metal disc operatively connected with the output thereof, an electromagnet adapted to act on said disc for braking same, an electric circuit feeding the electromagnet, means whereby the current flowing through said circuit is controlled by the angular location of the vertical lever and means operatively connecting the sun-and-planet gear with the carriage driving means at a speed increasing with the braking action exerted by the electromagnet for providing equilibrium between the stresses exerted by the carriage and by the spring on the sample.

8. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which the potentiometric system is inserted and energizing the motor, the speed of said motor depending on the energy flowing through the potentiometric system for the angular position assumed by the lever at the moment considered, an auxiliary switch actuated by the vertical lever when in its extreme position reached by it when the stress exerted by the spring has broken the sample, a further circuit controlled by said switch and means energized by said last mentioned circuit for returning the carriage and the spring controlling means into their starting position.

/ 9. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away'from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, an auxiliary switch controlled by the vertical lever in the rearmost position reached by it under the action of the spring when the sample breaks, a circuit in which said switch is inserted, means controlled by this last circuit adapted to release a ball at the breaking of each sample, a body provided with adjacent grooves adapted to receive said balls and means controlled by the circuit whereby each ball when released is directed into the groove corresponding to the stress exerted on the spring at the moment of the breaking of the sample that has produced the release of the ball considered.

10. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and auxiliary switch controlled by the vertical lever in the rearmost position reached by it under the action of the spring when the sample breaks, a circuit in which said switch is inserted, a recording system including a stylus and a chart and means controlling a circuit for controlling the relative movements of the stylus with reference to the chart in accordance with the stresses to which the spring is submitted at the moment of the breaking of a sample and means for shifing the chart with reference to the stylus through a given amount each time a sample is broken.

11. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and auxiliary switch controlled by the vertical lever in the rearmost position reached by it under the action of the spring when the sample breaks, a circuit in which said switch is inserted, a recording system including a chart, a punch adapted to move perpendicularly to the surface of the chart to perforate openings therein and to move perpendicularly to the length of the chart and to this first movement in accordance at each time with the tested value to be recorded, means controlling same at the breaking of a sample and means actuated by the movement of return to zero of the spring stretching means for making a 'sample tensioning direction, mansfcontrolling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means forrecording the elongations of each sample as functions of the forces applied thereto.

13. A, machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means for recording the elongations of each sample as functions of the forces applied thereto, said means including a horizontal arm carried pivotally by the carriage and adapted to assume a predetermined adjusted angular setting with reference to the direction of elongation of the sample, a series of rods bearing on said arm and lying horizontally in parallelism with said direction of elongation and switches associated with each horizontal rod for energization thereby when the corresponding rod drops off the forwardly travelling arm, circuits in which the corresponding switches are inserted and two meters energized by each circuit and adapted to record respectively a pulse at the dropping of the corresponding horizontal rod and a number of pulses corresponding to the duration of progression of the carriage, beyond the pointat which the corresponding rod has dropped.

14. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for 18 the angular position assumed at the moment considered, and means for recording and integrating at least one of the magnitudes, forces exerted and elongations obtained, throughout the testing of a'sample.

15. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor andlspeed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means for opening the clamps and means controlled by the return of the spring stretching means to zero adapted to control said clamp opening means.

16. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means, associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment consideredyand means for opening the clamps and means controlled by the return of the spring stretching, means to zero adapted to control said clamp opening means, thread laying means and means controlled by the end of the operative movement of said laying means and closing the clamps.

17. A machine for ascertaining the elongations of samples of thread or the likematerial comprising two clamps for the ends of the sample,

a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, aspringurging'the leverin a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means for giving each sample a predetermined tension before the beginning of its testing.

18. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means associated with the clamp secured to the vertical lever for removing the sample broken at the end of the test and means for controlling simultaneously the opening of last mentioned clamp and the removal of the broken sample through last mentioned means.

19. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, an auxiliary switch controlled by the vertical lever in the rearmost position reached by it under the action of the spring when the sample breaks, a circuit in which said switch is inserted, a recording system including a chart and to move perpendicularly to the length of the chart and to this first movement in accordance at each time with the tested value to be recorded, a punch adapted to move perpendicularly to the surface of the chart to perforate elongated openings therein, means controlling same at the breaking of a sample and means actuated by the movement of return to zero of the spring stretching means for making the chart be shifted longitudinally through a given amount after each perforation.

20. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, an auxiliary switch controlled by the vertical lever in the rearmost position reached by itunder the action of the spring when the sample breaks, a circuit in which, said switch is inserted and means energized by last mentioned circuit and controlling the return of the carriage and of the spring controlling means to their starting position and means for giving an increased speed to said return movement.

21. A machine for ascertaining the elongations of samples of thread or the like material comprising two clamps for the ends of the sample, a vertical pivoting lever to which one clamp is secured, a carriage to which the other clamp is rigidly secured, a spring urging the lever in a sample tensioning direction, means controlling the stretching of the.spring in accordance with a predetermined function of time, means driving the carriage radially away from the lever for tensioning the sample in opposition to the spring, an electric motor and speed reducing means associated therewith for controlling last mentioned means, a potentiometric system controlled by the Vertical lever when urged by the spring through predetermined angles, a circuit in which said potentiometric system is inserted and controlling the motor at a speed depending on the energy fed through the potentiometer for the angular position assumed at the moment considered, and means for adjusting the location of the vertical lever on a line parallel to the direction of movement of the carriage.

LOUIS FRANQOIS GUIMBRETIERE. EUGENE JEAN SOREZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date to 2,176,016 Sivertsen Oct. 10, 1939 2,350,722 Buckingham June 6, 1944 2,411,451 Demartini et al. Nov. 19, 1946 FOREIGN PATENTS 5 Number Country Date 257,634 Great Britain Apr. 21, 192 7 

